Transmission lines are known in which a tube of dielectric material has inner and outer metallic layers serving as the coaxial conductors thereof. In commonly owned U.S. Pat. No. 3,878,485, for example, there has been shown a transmission line of this description whose inner and outer layers are connected by soldering to respective leads of a two-wire branch line, one of these leads terminating in a plug traversing a peripheral bore in the dielectric tube.
In many instances, as in time-division-multiplex telephone (TDM) systems using pulse-amplitude modulation (PAM) to convey voice samples, parasitic storage of electrical energy in the transmission line causes objectionable cross-talk between adjacent time slots unless special measures, such as those described in the above-identified prior patent, are adopted. This calls for the use of coaxial conductors not only in the main transmission line but also in the associated branch lines.